Measuring angles

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Measuring angles

  1. 1. Measuring Angles
  2. 2. <ul><li>Angles are measured with a protractor </li></ul>
  3. 3. <ul><li>Let’s see some examples </li></ul><ul><li>Suppose you have to measure this angle: </li></ul>
  4. 4. <ul><li>Place the protractor in this way : </li></ul><ul><li>The centre of the protractor on the vertex of the angle </li></ul><ul><ul><li>The line through the centre of the protractor should be on top of one of the sides of the angle </li></ul></ul>centre
  5. 5. <ul><li>Read the measure at the corresponding scale </li></ul>38 centre
  6. 6. <ul><li>Let’s see another example: </li></ul>centre 54
  7. 7. You can use the protractor for drawing angles Let’s draw an angle of 120º With the ruler draw a line segment 120º Take away the protractor Place the protractor in this way: The centre of the protractor in one end of the line segment The line through the zeros on top of the line segmen t And draw a mark at 120 º 0 0 120 centre Draw a line through the centre and the mark
  8. 8. Classifying angles Right : 90º Acute : less than 90º Obtuse : more than 90º and less than 180º Straight : 180º Reflex : more than 180° but less than 360°
  9. 9. Supplementary angles 180º Supplementary angles add up to 180º
  10. 10. Complementary Angles Complementary angles add up to 90º 90 º

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